Thunderbird98 Posted January 29, 2021 Share Posted January 29, 2021 I just bought a Coco 2 (sadly only 16k). I would like to upgrade it to 64k, but I don't want to totally screw up my machine. I would also like to install extended color basic. Are there and tutorials on how I can do this? Quote Link to comment Share on other sites More sharing options...
bluejay Posted January 29, 2021 Share Posted January 29, 2021 Depends on what model your CoCo 2 is. There used to be a really good guide, but I can't find it anymore. This was all I could find after some quick googling: Quote 26-3026 This is the first model of CoCo 2. Built in the USA, it came equipped with 16 kilobytes of RAM, Color BASIC only, and the 'melted' keyboard. Most of its chips are socketed. This machine is based on the #8709416 PC board, and has a large, upright RF modulator with integrated TV channel 3/4 switch. Also characteristic of this machine is the use of a large power supply pass transistor (in a TO-3 package). The two 24-pin ROM sockets are located near the cartridge/system bus connector, and the eight RAM chips are located in a single row under the keyboard. (Note that this same model number has reportedly been found on larger, Korean-made CoCo models in Australia.) 26-3027 This machine is identical to the 26-3026, with the exception that it already has the Extended BASIC ROM factory-installed. To upgrade the 26-3026 or 26-3027 to 64 KB of RAM, it is necessary to replace the eight 8040517 chips with 4164 chips of 200 ns or better access time, and to solder a wire between the two pads labeled W1. W1 is located between U6 and U7. 26-3127 This is the first '64K Color Computer 2'. It contains the Extended BASIC ROM, the 'enhanced' keyboard, and 64 kilobytes of RAM (naturally). Otherwise, it is identical to the 26-3026/26-3027. Note that the RAM is soldered in place in those machines which were factory-equipped with 64K, making replacement thereof a bit more difficult if necessary. For this reason, the 26-3026 and 26-3027 variants are favorites of the author. 26-3134 This is the first Korean-made 16K Color BASIC CoCo 2. It uses the #20261043 circuit board, which differs considerably from that used in the earlier USA-made models. Virtually every component on the board has been relocated. The RF modulator is now a smaller unit, lying flat on the board rather than standing upright, and the channel 3/4 switch has been moved to the main board from the modulator. The positions of the various switches and connectors on the PC board (and therefore on the rear panel) differ from those of the previous machines as well. The RAM chips are located in two rows (one of five and one of three chips). This machine has a metal 'cage' surrounding the power transformer, which was not present in previous models. The power supply utilizes a cooler-running pass transistor (in a TO-220 package). The RF modulator, power transformer, pass transistor, and switch/jack location characteristics of this machine persist on all subsequent models. Most chips are soldered in place on this and all subsequent boards as well. 26-3136 This machine is identical to the 26-3134, but with the Extended BASIC ROM factory-installed. To upgrade the 26-3134 or 26-3136 to 64 KB of RAM, it is necessary to replace the eight 8040517 chips with 4164 chips of 200 ns or better access time, and to solder a wire between the two pads labeled J1. J1 is located next to IC7. 26-3134A This is the next Korean 16K Color BASIC CoCo 2. It utilizes a #20261044 circuit board, which differs considerably from the previous versions. This board's RAM is in the form of two socketed 4416 chips. The preferred 64K upgrade for this board involves replacing them with two 4464 chips. However, the option exists (by means of several special connectors on the board) of a factory upgrade consisting of eight 4164 chips on a daughterboard. Legend has it that the option of using either 4164s or 4464s was incorporated for economic reasons (the pricing and availability of RAM were quite unstable when these machines were manufactured). Additionally, this board introduces the use of a single 28-pin ROM socket. A 24-pin ROM containing only Color BASIC 1.3 shipped in that socket in this model. With appropriate jumpering, this socket is able to accept a 27128 EPROM. 26-3136A This machine is the 16K Extended BASIC version of the 26-3134A. It uses a single 28-pin, 16-kilobyte ROM containing both Color BASIC and Extended BASIC. 26-3134B This is the last Korean 16K Color BASIC model. It uses the #20261058 circuit board, which is similar to the #20261044 board. It uses two 4416 RAM chips and a 24-pin Color BASIC 1.3 ROM in a 28-pin socket as well. However, in addition to the 4416/4464 sockets and special daughterboard connectors, there are pads on the board allowing direct factory installation of eight 4164 chips. This is also the board which contains the newer 6847T1 VDG chip (which is not pin-compatible with the earlier 6847). 26-3136B This machine is the Extended BASIC version of the 26-3134B. To upgrade a 26-3134A, 26-3136A, 26-3134B, or 26-3136B to 64 KB of RAM, it is necessary to replace the two 4416 chips with 4464 chips of 200 ns or better access time, and to solder a jumper across the two pads labeled RAM SIZE 64K. The RAM SIZE 64K jumper is located next to IC4. 26-3127B The last model number associated with the 64K Extended BASIC CoCo 2, this is an odd one indeed. The author has no less than three distinctly different machines, each bearing this exact model number. One is a USA-made TRS-80 with a #20261044 board and a 6847, one is a USA-made Tandy with a #20261058 board and a 6847T1, and one is a Korean-made Tandy with a #20261058 board and a 6847T1. Contrary to some rumors, the presence of the 'B' in the model number does NOT necessarily indicate the presence of a 6847T1. As noted previously, the Tandy label appears to be the best external indication thereof. One absolutely accurate method of determining if one is present is to type a '0' (zero) on an operating machine. If the resulting character on the screen is displayed with a slash through it, the machine in question has a 6847T1. Hope this helps. Quote Link to comment Share on other sites More sharing options...
Thunderbird98 Posted January 29, 2021 Author Share Posted January 29, 2021 I have the 26-3134. Sounds like it will require soldering. Ugh. Quote Link to comment Share on other sites More sharing options...
MrDave Posted January 29, 2021 Share Posted January 29, 2021 Your ram upgrade is easy .. only 2 chips to replace and they are not hard to find.. as for the extended basic ( a must have ) there are a few jumpers to solder.. i can provide you with a eprom if needed .. If you know someone good at soldering get their help or ..using a fine tip soldering iron do some practice then solder your jumpers Quote Link to comment Share on other sites More sharing options...
Thunderbird98 Posted January 29, 2021 Author Share Posted January 29, 2021 Nice. I have someone who I'm going to ask to help me. I just need to know where I can buy those chips. Also, @MrDave if you are offering an eprom, I would be happy to buy one. Quote Link to comment Share on other sites More sharing options...
MrDave Posted January 29, 2021 Share Posted January 29, 2021 Sure , I can make a eprom .. usually 5$ cdn to 2$ shipping.. make sure you have the correct ,model.. right now you should have a 24 pin rom in a 28 pin socket if we are talking about thw correct machine.. do you need ram as well ? Quote Link to comment Share on other sites More sharing options...
Thunderbird98 Posted January 29, 2021 Author Share Posted January 29, 2021 (edited) I have a 26-3134, and I think it has a 24 pin socket, I'll have to check. Yes I would like enough ram to upgrade to 64k. How much will the eprom cost? Edited January 29, 2021 by Thunderbird98 Quote Link to comment Share on other sites More sharing options...
MrDave Posted January 29, 2021 Share Posted January 29, 2021 (edited) Eprom is 5$ plus 2$ shipping cdn Post a picture of your coco motherboard Edited January 29, 2021 by MrDave Quote Link to comment Share on other sites More sharing options...
Thunderbird98 Posted January 29, 2021 Author Share Posted January 29, 2021 This is my motherboard, RAM and eprom slot. Quote Link to comment Share on other sites More sharing options...
MrDave Posted January 29, 2021 Share Posted January 29, 2021 Ahh ok you need 8 1x64 drams and a 24 pin eprom Quote Link to comment Share on other sites More sharing options...
MrDave Posted January 29, 2021 Share Posted January 29, 2021 Not much soldeting to do .. just solder a little wire on j1 ( bottom left ..says 64k ) a lttlecwire soldered between those pins and pop in the chips and eprom you are good to go. Quote Link to comment Share on other sites More sharing options...
MrDave Posted January 30, 2021 Share Posted January 30, 2021 Like this.. for ram Quote Link to comment Share on other sites More sharing options...
Thunderbird98 Posted January 30, 2021 Author Share Posted January 30, 2021 Thank you so much! Quote Link to comment Share on other sites More sharing options...
bluejay Posted February 10, 2021 Share Posted February 10, 2021 http://users.digitalindigo.net/techno/coco2.html I found the link I mentioned before in an old status update of mine. Not sure if it'll help you anymore though. Quote Link to comment Share on other sites More sharing options...
Thunderbird98 Posted February 20, 2021 Author Share Posted February 20, 2021 thanks I'm kind of putting this project on hold. I'm only a high school student and I'm not going to be working for another few months, so I might post again when I'm ready to invest more time and money. Quote Link to comment Share on other sites More sharing options...
MrDave Posted February 21, 2021 Share Posted February 21, 2021 My first coco was a 16k. It will be limited but still alot you can do.. and you can always program on a emulator like xroar or vcc. Quote Link to comment Share on other sites More sharing options...
J Dee Posted March 9, 2021 Share Posted March 9, 2021 On 1/29/2021 at 3:48 PM, MrDave said: Sure , I can make a eprom .. usually 5$ cdn to 2$ shipping.. make sure you have the correct ,model.. right now you should have a 24 pin rom in a 28 pin socket if we are talking about thw correct machine.. do you need ram as well ? I am in the market for ram, I'm currently 16k but would do the 64k. 26-3136 machine with 8040517 ram currently installed. Where is the best place to grab this? Quote Link to comment Share on other sites More sharing options...
MrDave Posted March 10, 2021 Share Posted March 10, 2021 Ebay is pretty good.. unless you know a good electronics house Quote Link to comment Share on other sites More sharing options...
MrDave Posted March 10, 2021 Share Posted March 10, 2021 You can get get 10 chips on ebay under 20$ cdn Quote Link to comment Share on other sites More sharing options...
ColorComputerStore Posted March 16, 2021 Share Posted March 16, 2021 I have both Extended BASICs available for sale. Those that need 24 pin and those that need 28 pin. http://www.ebay.com/itm/264912430491 http://www.ebay.com/itm/264973699291 Send me a note on ebay with 'Atari Forum' and I'll apply a promo code. I also sell replacement case badges for the CoCo: https://www.ebay.com/sch/colorcomputerstore/m.html?_nkw=&_armrs=1&_ipg=&_from= I am happy to walk you through a zoom meeting to help you upgrade your RAM and BASIC. If you are near 06096 zip code, I am also happy to install all for free. Regards. 1 Quote Link to comment Share on other sites More sharing options...
Marlim93 Posted September 25, 2021 Share Posted September 25, 2021 Hi, thanks for sharing your lore about this archaic machine. I just got a 26-3134A machine, 16K, single 24-pin rom in a 28-pin socket. Got an EPROM burner (first time I’ll use it), got a couple of EPROMS (27128 16K if I remember correctly) and two 4464 chips… could you please confirm if I have all the ingredients for the cooking recipe? I still have to locate a reliable ROM for Extended Basic on the web (I saw a site that listed a Coco2b ROM, must be that?) and I need to learn how to rewire an EPROM socket to convert it from standard 28-pin to the Coco2 24 wiring scheme… this is actually what I’m dreading the most. Any tips ? Thanks for your help !!! Quote Link to comment Share on other sites More sharing options...
MrDave Posted September 25, 2021 Share Posted September 25, 2021 If your coco2 has the 28 pin socket with a 24 pin rom in it ..you need to move a bunch of jumpers from the 64 to 128 , ( 128 k bit is a 16k rom , 128/8 ) then you have to burn the 2 rom images on the same eprom. The extended basic in the lower half and the regular basic in the top half...make sense. ? Quote Link to comment Share on other sites More sharing options...
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